Priority based methods and apparatus for transmitting accurate emergency location idenitfication numbers (ELINs) from behind a multi-line telephone system (MLTS)

ABSTRACT

Methods for accurate transmission of ELIN/callback number from an emergency caller calling from behind a PBX/MLTS include prioritizing the emergency call, assigning a port equipment number to each device/trunk of the PBX/MLTS and associating ports/devices with ELINs and callback numbers. The apparatus of the invention detects an emergency number, assigns the call priority, and uses the port/device number to determine the ELIN/callback number and properly transmit the ELIN/callback number.

[0001] This application is related to co-owned co-pending applicationSer. No. ______ entitled “Methods And Apparatus For TransmittingAccurate Emergency Location Identification Numbers (ELINs) From Behind AMultiline Telephone System (MLTS) Utilizing Port Equipment Numbers”;co-owned co-pending application Ser. No. ______ entitled “Methods AndApparatus For Transmitting Over A Private Network Accurate LocationIdentification Numbers (ELINs) From Behind A Multiline Telephone System(MLTS)”; co-owned co-pending application Ser. No.______ entitled“Methods And Apparatus For Transmitting Accurate Emergency LocationIdentification Numbers (ELINs) From Behind A Multi-Line telephone System(MLTS) After An Emergency Caller Disconnects”; co-owned co-pendingapplication Ser. No. ______ entitled “Methods And Apparatus ForTransmitting Accurate Emergency Location Identification Numbers (ELINs)After An Emergency Caller Disconnects”; co-owned co-pending applicationSer. No. ______ entitled “Methods And Apparatus For Dialing An EmergencyTelephone Number From A Teleworking Client Remotely Coupled To A PBX”;and co-owned co-pending application Ser. No. ______ entitled “System orDialing An Emergency Telephone Number From A Teleworking Client RemotelyCoupled To A PBX”, the complete disclosures of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to telecommunications systems, especiallyPBX/Server systems, also referred to as Multi-Line Telephone Systems(MLTS). Specifically, the invention relates to completing an emergency,e.g. 911, call from a station/device behind a MLTS to a public networkemergency facility and delivering precise location information of thecaller based on a port equipment number associated with the port fromwhich the emergency call originated.

[0004] 2. Brief Description of the Prior Art

[0005] When a caller calls an emergency number, e.g. 911, the call isrouted to a Public Safety Answering Point (PSAP). In some jurisdictions,regulatory agencies require that the caller's telephone number/callbacknumber and/or precise physical location referred to as LocationIdentification Number (ELIN), be automatically provided to the PSAP.This information is used to locate the caller and to call back to thecaller should there be a disconnect.

[0006] A caller identification (i.e., telephone number and ELIN) may bedelivered to the PSAP either in-band (e.g., using DTMF signaling) orout-of-band (e.g., using ISDN signaling) depending on the type of trunkcircuit employed. For residential callers Caller ID number is sufficientfor the PSAP. For PBX/server service many users, e.g., commercialcallers, hotel guests; an ELIN is required for this complex environment,for example, street address, floor number, room number, desk number. Insome cases, the ELIN is geodetic, i.e. includes earth coordinates or GPSdata.

[0007] Modern PBX/MLTS systems provide many new features to accommodatethe way modern businesses operate. For example, employees may beassigned personal identification numbers (PINs) that are used by thePBX/MLTS to identify the employee and assign a telephone number tohim/her. Further, for example, if an employee is assigned to a differentlocation in the building, an automatic relocation feature can beactivated using the PIN to reassign the employee's telephone number tothe new location.

[0008] Another feature of PBX/MLTS systems is that some telephonesconnected to the PBX/MLTS system may not be provided with the ability toreceive direct (inward) dialed calls. For example, in a hotel,telephones in rooms are typically not capable of receiving a directinward call from outside the hotel, therefore they have no known CallerID to identify them to the PSAP. no known Caller ID to identify them tothe PSAP.

[0009] Still another feature of modern PBX/MLTS systems is that it ispossible to make many or even all telephone lines available for use bymultiline devices connected to the system. Thus, a caller from behindthe PBX/MLTS system may be identified by many different telephonenumbers.

[0010] All of these features of modern PBX/MLTS systems present problemsfor transmitting call back number and ELIN to a PSAP in an emergencycall. In many situations, the only callback number provided from thePBX/MLTS system is the main directory billing number. In situationswhere the caller has utilized the automatic relocation feature of thePBX/MLTS system, the caller will be identified by employee PIN but notby a specific location. In situations where the caller has no directinward call receive capability, the PSAP cannot call back the caller inthe event of a disconnect. In the situation of a call from a multilinedevice, the telephone number from which the emergency call is made maynot be the primary number for the caller and a return call to thatnumber may cause a different device to ring rather than the caller'sdevice. Moreover, the number used by the emergency caller may beassociated with a ELIN which is not the caller's ELIN.

SUMMARY OF THE INVENTION

[0011] It is therefore an object of the invention to provide methods andapparatus for accurately reporting the ELIN of an emergency callerbehind a PBX/MLTS system to a PSAP.

[0012] It is also an object of the invention to provide methods andapparatus for operating a PBX/MLTS system wherein emergency calls aregiven priority treatment over non-emergency calls (e.g., when al trunksbusy conditions exists, first available trunk is awarded to an emergencycall); and to accurately report the callback number of an emergencycaller behind a PBX/MLTS system to a PSAP.

[0013] It is another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP that do notinterfere with the features of the PBX/MLTS.

[0014] It is yet another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP wherein thegranularity of ELIN can be determined by the administrator of thePBX/MLTS.

[0015] It is another object of the invention to provide methods andapparatus for accurately reporting the ELIN of an emergency callerbehind a PBX/MLTS system to a PSAP that includes identifying the type ofELIN, e.g. geodetic or non-geodetic.

[0016] It is still another object of the invention to provide methodsand apparatus for managing a database of ELINs and callback numbersassociated with a PBX/MLTS system.

[0017] It is yet another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP wherein multipleemergency numbers are supported.

[0018] It is another object of the invention to provide methods andapparatus for operating a PBX/MLTS system wherein emergency calls aregiven priority over non-emergency calls.

[0019] It is still another object of the invention to provide methodsand apparatus for accurately reporting the ELIN and callback number ofan emergency caller behind a PBX/MLTS system to a PSAP wherein the callis routed over a private network before reaching the public network.

[0020] It is yet another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP using ISDN ornon-ISDN trunking facilities.

[0021] In accord with these objects which will be discussed in detailbelow, the methods according to the invention include assigning a portequipment number (PEN) to each port associated with the PBX/MLTS system,maintaining a database of ELIN and callback numbers associated withPENs, identifying an emergency number when it is dialed, invoking anemergency service routing upon detection of a dialed emergency number,associating the PEN with the dialer of the emergency number, retrievingthe ELIN and callback number (and optionally other information) from thedatabase, and transmitting the ELIN (according to PRI standards i.e.,Generic Information IE) and callback number to the PSAP.

[0022] The apparatus of the invention includes database managementmeans, emergency number detection means, call routing means, ISDN andnon-ISDN signaling means. The invention may be configured so that eitherthe callback number, the ELIN, or both are transmitted to the PSAP.Further, the invention may be configured to recognize multiple emergencynumbers and to give emergency calls priority over non-emergency calls.

[0023] The specificity of the ELIN can be determined by the systemadministrator and additional information may be associated with theELIN. The call routing and signaling means are capable of routing theemergency call through multiple PBX/MLTS systems before reaching thepublic network.

[0024] Additional benefits and features of the invention will beapparent from the following detailed description taken together with theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a high level illustration of a PBX/MLTS system accordingto the invention in the process of making an emergency call;

[0026]FIG. 2 is a high level block diagram of the apparatus of theinvention;

[0027]FIG. 3 is a high level block diagram of the call processor anddevice handler of FIG. 2;

[0028]FIG. 4 is a high level diagram of the database structure accordingto the invention; and

[0029]FIG. 5 is a high level flow chart illustrating the methods of theinvention.

DETAILED DESCRIPTION

[0030]FIG. 1 provides by way of example an overview of an emergency callas originated in a private network (via MLTS 10) on Customer PremiseEquipment (CPE) 12.

[0031] According to the invention in the context of the aforementionedexample, the call may be routed directly to the public network 14 orfirst transit over the private network (via one or more other MLTS 16)to a far end “hop off” to the public network 14. The private networkroute may include ISDN (e.g., QSIG/PSS1) or analog tie trunks.

[0032] Furthermore, according to the invention, the ELIN/callback numberis sent with the emergency call over the private network 7 then to thepublic gateway MLTS 16. The encoding of the DTMF tones over analog tieand facility IE APDU are implementation dependent private extensions ona private network. The MLTS 10 or 16 may send the emergency call andELIN/callback number via an ISDN PRI or analog CAMA (centralizedautomatic message accounting) trunk to the public network 14. In eithercase, the Central Office 18 receives the information and routes the callto the proper 911 Tandem Office 20 which routes the call to theappropriate PSAP 22, 24.

[0033] A special Automatic Location Identification database (ALI DB) 26is maintained to match the received ELIN and/or Callback number anddisplay associated information at the PSAP. It is the MLTSadministrator's responsibility that the caller information be correctlylisted in the ALI DB.

[0034] Referring now to FIG. 2, an MLTS 10 according to the inventionincludes a database 30, a database administration module 32, a callprocessing module 34, a device handler 36, an emergency services (ES)module 38, and a dependability module 40. The dependability module 40provides call recovery functions in the event of an equipment failure.

[0035] According to the presently preferred embodiment, the trunk sideof the MLTS 10 includes an ISDN Primary Rate Interface 42, a privateISDN interface 44 for coupling to other customer equipment, and ananalog interface 46 for coupling to either the public network or theprivate network.

[0036] As mentioned hereinbefore, on the user/line side of the MLTS 10,each user equipment is coupled to a unique port and each port isassigned a unique port equipment number (PEN) 48. As described in moredetail below with reference to FIG. 5, when an emergency call is dialed,call processing FIG. 2 34 recognizes the digits and invokes emergencyservices 38 which, using the PEN 48 retrieves the appropriateinformation from the database 30. The device handler 36 providesnecessary signaling/outpulsing depending on the type of trunk used. Theinvention doe not preclude the ability to assign incoming trunks (thatare emergency calls) with PENs to the ELIN database.

[0037] Referring to FIG. 3, the call processing module 34 includes aleast cost routing (LCR) module 34 a, an invoke ES module 34 b, and abasic call processing module 34 c. The device handler 36 includes aprivate signaling module 36 a (e.g., analog tie DTMF, QSIG), a publicsignaling module (e.g., CAMA, primary rate interface (PRI)) 36 b throughwhich calls are setup and ELIN/callback number data is transmitted vialink 36 c or 36 d.

[0038] When the emergency caller 48 dials (e.g., 911), a connect requestinternal message is sent to the call processing module 34. The emergencydigits are recognized by least cost routing (LCR) 34 a and emergencyservices (ES) 38 is invoked for this call.

[0039] According to the invention, the emergency digits are recognizedat 34 b depending on how the unit has been programmed. For example, anindicator on one or more digit patterns in the dial plan flags this asan emergency call when the digits match.

[0040] This mechanism “triggers” ES processing 38. ES 38 performs allthe necessary functions to deliver this call as a priority emergencycall with correct ELIN and Callback Number to the basic call processor34 c. Normal processing resumes for trunk selection, basic callestablishment sending an internal message with the ELIN and CallbackNumber to Device Handler 36.DH 36 formats the call informationappropriately for the trunk which has been awarded.

[0041] When the trunk is a private trunk 36 d, the ELIN and/or CallbackNumber (calling party number CPN) are formatted in a proprietaryencoding. When the trunk is a public trunk 36 c, the ELIN and CallbackNumber are formatted according to the trunk protocol required (e.g.,CAMA, PRI). The trunk facilities may be non-ISDN with DTMF signaling orISDN where the ELIN and Callback Number are encoded in the SETUP message(Generic Information IE) sent on the signaling channel.

[0042]FIG. 4 is an example of the internal tables associated with thedatabase of the invention. Table 1 50 is a PEN-to-ELIN index table andTable 2 52 is a ELIN index-to-ELIN and callback number table.

[0043] Referring now to table 1 50, the first column 54 is a list of allPENs which have a device/trunk that can originate an emergency call. Thesecond column 56 identifies all of the devices sharing the same PEN(e.g., multi-drop configuration) and the third column 58 provides anindex number to it's assigned ELIN/Callback entry for each device/trunk.The invention does not preclude or limit the usage of device or trunktypes (e.g., analog POTS, IP phone, workstation).

[0044] Typically, each PEN is associated with only one end device andtherefore associated with only one ELIN index value shown in the thirdcolumn. Therefore, the device column 56 is optional/not used. The ELINindex value is a pointer into table 2. The system administrator assignsan index to each PEN or device within a PEN (i.e., multi-drop).

[0045] The optional device column 56 may consist of several entries,each associated with that same PEN value. This allows for multiple enddevices to be configured and connected to one jack and therefore, onePEN. Each device specified has it's own associated ELIN index valuewhich may be different from another device on that same PEN. When ESretrieves an emergency call's PEN, when there is more than one enddevice, it must be able to identify which logical (or physical) deviceinitiated the call (i.e., 1−n) and use both the PEN and device number toselect the associated ELIN index.

[0046] Table 1 may be any length. The PEN field may optionally be set upto represent a range of PENs rather than a single PEN. The format of thePEN is implementation-dependent. Optional fields may further identifythe PEN/device.

[0047] Table 2 52 is, for example, an indexed table where a list of theELIN index numbers is represented in the first column 60, and the tableincludes a list of the associated ELINs in the second column 62, a ELINtype indicator in the third column 64, the callback number associatedwith the ELIN in the fourth column 66 at other optional fields such as,a text description of the ELIN in the fifth column 68, and a populationfield in the sixth column 70.

[0048] In this table example the ELIN index number obtained from table 1is used to access the corresponding index value table entry in the firstcolumn of Table 2. This table entry provides the actual 10-digit NANP(North American Numbering Plan) ELIN assignment as seen in the secondcolumn. The invention does not preclude the usage of another type oftable access nor is limited with it's contents (e.g., otheridentification information).

[0049] The assignment of ELIN values are the responsibility of the CPEadministrator. The ELIN values are reported to the PSAP who should havea matching ELIN value in their ALI database with associated locationinformation.

[0050] The ELIN type indicator is applicable when a PRI connection tothe PSAP is used. The ELIN type value correlates to the GenericInformation Information Element (IE) octet 3 (bits 5-1) Type ofInformation as defined in the American National Standard T1.628-2000.

[0051] The two current defined values represent whether the informationadministered in the ELIN field is Geodetic or non-Geodetic information.The Callback# field 66 is a 10-digit NANP public network number whichcan be used by the PSAP to dial the caller back should the connection bebroken. The CPE administrator designates which phone number is to beused as the Callback Number associated with this ELIN, typically it'sDID number if available or a phone relatively close to the physicallocation of the calling location or possibly a receptionist.

[0052] Optional fields, such as the Description field 68 is a commentsfield used by the local administrator to help identify the ELIN. The POP(for population) field 70 is an internal register which is incrementedand decremented each time a PEN is assigned/deassigned this table entryindex in the PEN-to-ELIN table via an administrative action. Therefore,it represents the number of PENs that are currently assigned to thisparticular ELIN and Callback Number. The content of Table 2 iscompletely flexible. ELINs and Callback Numbers can appear multipletimes in the table. The size of the table is implementation-dependent.

[0053] Tables 1 and 2 reside in each MLTS in a network. The ESprocessing and ELIN/Callback Number retrieval occurs at the originatingMLTS. The resulting call information is transmitted either to the publicnetwork or first over the private network for far end hop off to thepublic network. This does not preclude the destination of an emergencycall being on-site with delivery of ELIN and Callback Number to a localemergency call operator. This may be desired when the organizationresponsible for the MLTS screens all emergency calls at a designatedcentral location or when the organization has its own emergencypersonnel such as security guards and medical personnel.

[0054]FIG. 5 is an example of a high level flow chart illustrating thelogic of the processing of an emergency call according to the invention.Starting at 72, a station user dials an emergency number (e.g., 911).The LCR processes the digits at 74 and recognized the digits asrepresenting an emergency call at 76. LCR invokes ES at 78. ES (80-86)assigns the call priority at 80, retrieves the PEN/device number at 82,obtains ELIN index from table 1 at 84, and obtains ELIN, type andcallback number from table 2. ES turns over the information to thedevice handler which formats the information at 88 and proceeds withnormal call processing at 90.

[0055] Though not illustrated in FIG. 5, if a matching PEN cannot befound, the invention may optionally report the missing PEN, exit ES, andcontinue with regular call processing. If a matching PEN was found andno device number applies, ES retrieves the ELIN index associated withthis PEN. If a matching index is not found in table 2, the invention mayoptionally report the missing index and PEN, exit ES, and continue withregular call processing.

[0056] There have been described and illustrated herein methods andapparatus for precise reporting to a PSAP of an accurate ELIN/callbacknumber from an emergency caller calling from behind a PBX/MLTS. Whileparticular embodiments of the invention have been described, it is notintended that the invention be limited thereto, as it is intended thatthe invention be as broad in scope as the art will allow and that thespecification be read likewise. It will therefore be appreciated bythose skilled in the art that yet other modifications could be made tothe provided invention without deviating from its spirit and scope as soclaimed.

What is claimed is:
 1. A method for processing an emergency call madefrom behind a PBX/MLTS, said method comprising the steps of: a) withinthe PBX/MLTS determining whether dialed digits represent an emergencynumber; and b) assigning priority within the PBX/MLTS to a calldetermined to be an emergency call.
 2. A method according to claim 1further comprising the steps of: c) storing a port equipment number foreach device/trunk in the PBX/MLTS; and d) associating an emergencylocation identification number (ELIN) with each port equipment number.3. A method according to claim 2 further comprising the steps of: e)determining from which port the emergency call originated; and f)transmitting to a public safety answering point the ELIN associated withthe port from which the emergency call originated.
 4. A method accordingto claim 1 further comprising the steps of: c) storing a port equipmentnumber for each device/trunk in the PBX/MLTS; and d) associating acallback number with each port equipment number.
 5. A method accordingto claim 4 further comprising the steps of: e) determining from whichport the emergency call originated; and f) transmitting to a publicsafety answering point the callback number associated with the port fromwhich the emergency call originated.
 6. A method according to claim 1further comprising the steps of: c) storing a port equipment number foreach device/trunk in the PBX/MLTS; and d) associating an emergencylocation identification number (ELIN) and a callback number with eachport equipment number.
 7. A method according to claim 6 furthercomprising the steps of: e) determining from which port the emergencycall originated; and f) transmitting to a public safety answering pointthe ELIN and the callback number associated with the port from which theemergency call originated.
 8. An apparatus for processing an emergencycall made from behind a PBX/MLTS, said apparatus comprising: a) meanswithin the PBX/MLTS for determining whether dialed digits represent anemergency number; and b) means for assigning priority within thePBX/MLTS to a call determined to be an emergency call.
 9. An apparatusaccording to claim 8 further comprising: c) means for storing a portequipment number for each device/trunk in the PBX/MLTS; and d) means forassociating an emergency location identification number (ELIN) with eachport equipment number.
 10. An apparatus according to claim 9 furthercomprising: e) means for determining from which port the emergency calloriginated; and f) means for transmitting to a public safety answeringpoint the ELIN associated with the port from which the emergency calloriginated.
 11. An apparatus according to claim 8 further comprising: c)means for storing a port equipment number for each device/trunk in thePBX/MLTS; and d) means for associating a callback number with each portequipment number.
 12. An apparatus according to claim 11 furthercomprising: e) means for determining from which port the emergency calloriginated; and f) means for transmitting to a public safety answeringpoint the callback number associated with the port from which theemergency call originated.
 13. An apparatus according to claim 8 furthercomprising: c) means for storing a port equipment number for eachdevice/port in the PBX/MLTS; and d) means for associating an emergencylocation identification number (ELIN) and a callback number with eachport equipment number.
 14. An apparatus according to claim 13 furthercomprising: e) means for determining from which port the emergency calloriginated; and f) means for transmitting to a public safety answeringpoint the ELIN and the callback number associated with the port fromwhich the emergency call originated.